1. Field of the Invention
The present invention relates to an image forming apparatus that measures the imaging performance of visible image forming means in accordance with the start of power being supplied from a power source, and that executes an imaging condition setting control for setting imaging conditions in response to the measured result.
2. Description of the Related Art
In image forming apparatuses of this type an imaging condition setting control is executed to measure the imaging performance of visible image forming means immediately following the switching ON of a power source or immediately following reversion from an energy saving mode at a prescribed timing such as, for example, when a predetermined number of printed copies have been produced. The energy save mode constitutes an image forming command standby mode occurring in a state in which, when image forming commands such as a copy start button operation or a print command signal have not been implemented for at least a prescribed period, the power supply to a heating heater of a fixing device or the like is interrupted.
A known image forming apparatus in which this kind of imaging condition setting control is executed is described in Japanese Unexamined Patent Application No. 2003-345180. In this image forming apparatus the following process controls are executed as imaging condition setting controls. That is to say, first of all a plurality of patch latent images of different optical write intensity and shape established in advance are formed on a photosensitive body, and the electric potential of these patch latent images is detected by an electric potential sensor. These patch latent images are developed by a development apparatus to produce a plurality of patch toner images that serve as reference images, and the quantities of toner affixed per unit surface area to each patch toner image is detected by an optical sensor. Next, the imaging performance of visible image forming means configured from the photosensitive body, optical write device and development apparatus and so on is determined in accordance with the relationship between the electric potential of the patch latent images and the quantities of toner affixed to the patch toner images. Upon measurement of the imaging performance of visible image forming means in this way, imaging conditions such as control target values for the uniform charging potential of the photosensitive body, the development bias, the optical write intensity on the photosensitive body and the toner density of the developer are set. As a result of a suppressing of the fluctuations in imaging density or gradient reproducibility which are attributable to fluctuations in the environment (temperature and humidity) and toner characteristics (fluidity and bulk density and so on) afforded by this imaging condition setting control, high quality images can be stably formed for a long period.
A further process control executing condition considered in this image forming apparatus described in Japanese Unexamined Patent Application No. 2003-345180 immediately following switching ON of the power source or immediately following reversion from the energy save mode is the temperature of the fixing roller. This condition is considered with a view to avoiding a situation where the user is forced to wait an unnecessarily long time due to a process control being needlessly executed. More specifically, if the fixing roller exceeds a predetermined temperature (for example, not less than 50° C.) immediately following switching ON of the power source or immediately following reversion from the energy save mode, the period of time that the power source is OFF and the energy save mode is executed is very short (for example, several minutes). Marked fluctuations in the environment or the toner characteristics are unlikely to occur in such a short time. Accordingly, the change in imaging performance from the period immediately prior to interruption to the power source or immediately prior to transition to the energy save mode is essentially negligible. If a process control were to be nonetheless executed the user would be forced to wait unnecessarily. Thereupon, when the fixing roller exceeds a predetermined temperature immediately following switching ON of the power source or immediately following reversion from the energy save mode there is no process control executed. According to this configuration, the occurrence of the user being made to wait unnecessarily can be suppressed.
However, the inventor of the present invention discovered through testing that, even with this configuration, the user was sometimes forced to wait unnecessarily. More specifically, over a medium period of power source cutoff time or energy save mode execution such as between several tens of minutes and several hours there were sometimes insignificant fluctuations in the environment and toner characteristics. Accordingly, in this case it is also desirable for the executing of a process control immediately following switching ON of the power source or immediately following reversion from the energy to be omitted. However, over a medium period of power source cutoff time or energy save mode execution time the temperature of the fixing roller drops to about room temperature. Accordingly, the process control is executed and the user is forced to wait unnecessarily.
Notably, accompanying the demand for improved energy saving that has arisen in recent years, many image forming apparatus specifications have been designed so that a transition to the energy save mode occurs simply as a result of an image forming command having not been received for a very short time such as for several minutes. Accordingly, the user is frequently made to wait unnecessarily.
In addition, a user with a strong energy saving consciousness will switch the power source switch to OFF each time they complete a print operation. A user of this type is also frequently made to wait unnecessarily.
Apart from the user being forced to wait unnecessarily when an unnecessary imaging condition setting control is executed, the lifespan of visible image forming means is reduced and the image forming agents such as toner are needlessly consumed. This is because, to form the reference visible images such as the patch toner images for the imaging condition setting control, visible image forming means is actuated and image forming agents are consumed.
Almost all conventional image forming apparatuses in which an energy save mode is executed comprise a timer function for ascertaining whether the time since an image forming command was received exceeds a prescribed time. However, the energy save mode execution time and power source cutoff time cannot be ascertained utilizing this timer function. The timer function cannot be utilized for the energy save mode execution time and power source cutoff time because the power source supply to the timer circuit and control unit is cutoff at these times.
Technologies relating to the present invention are disclosed in, e.g.,
Japanese Unexamined Patent Application No. H11-160921, Japanese Unexamined Patent Application No. 2003-177638 and Japanese Unexamined Patent Application No. 2004-013101.